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Lick Observatory. Time exposure image showing star trails over a telescope dome at the Lick Observatory on Mount Hamilton in California, USA. In the foreground are trails from red flashlights carried by astronomers so that their night vision is not affected. Completed in 1888 at an altitude of 1280 meters, Lick was the world's first permanent mountaintop observatory. Its location provided excellent viewing conditions for years until light pollution from the nearby city of San Jose began to interfere with results. In 1997 the observatory is operated by California University. Star trails are caused by what seems to be the motion of the stars due to the rotation of the Earth about its axis. (1996)